Remote convenience systems are known in the art. Such remote convenience systems permit remote control of certain functions. One type of a remote convenience system is for remotely controlling vehicle functions. Other example types of remote convenience systems include garage door opener systems and entry light activation systems.
Examples of remotely controlled vehicle functions include locking and unlocking of one or more vehicle doors. A remote convenience vehicle system that permits remote locking and unlocking functions is commonly referred to as a remote keyless entry ("RKE") system. Remote convenience vehicle systems may provide for control of other vehicle functions.
Known remote convenience vehicle systems include a receiver/controller mounted in an associated vehicle and at least one portable hand-held transmitter located remote from the receiver/controller. Each transmitter is provided with one or more manually actuatable switches. Each switch is associated with a remote control vehicle function to be performed. The transmitter includes circuitry that responds to the actuation of each switch to transmit a message in the form of a digital signal.
The receiver/controller is configured to receive the transmitted signal and to determine the requested remote control function. Also, the receiver/controller is operatively connected to one or more vehicle systems that perform the function that are properly remotely requested.
To ensure that the remote function request is proper (i.e., authentic), known remote convenience vehicle systems use security codes or keys that accompany the function request message in the transmitted signal. In one known type of remote convenience vehicle system, a rolling code algorithm is performed to routinely modify the security key utilized within the system. Specifically, a rolling code algorithm is performed within the receiver/controller to determine a current security key, and a congruent rolling code algorithm is performed within the hand-held transmitter to also determine the same current security key.
Upon receipt of a transmitted signal containing a security key, the receiver/controller compares the key of the received signal with the key determined within the receiver/controller. If the received key is valid (i.e., the keys match), the receiver/controller causes performance of the requested function.
It is possible that the security key at the hand-held transmitter may become out of synchronization with the security key at the receiver/controller. One way that loss of synchronization can occur is if the hand-held transmitter changes the security key in response to actuation of a switch, but the receiver/controller does not receive the transmitted signal. Thus, the receiver/controller is "unaware" of the transmitted signal and is unaware of the security code change at the hand-held transmitter. It may even be possible to change the security key at the hand-held transmitter multiple times via multiple actuations of the switch while the security key at the receiver/controller remains unchanged.